1. Field of the Invention
The present invention relates to wireless keyboards for use in a data processing system and, more specifically, to antenna systems for wireless keyboards for use in a data processing system.
2. Description of the Related Art
Wireless keyboards for use with personal computers are known. Specifically, wireless infrared keyboards for use with personal computers are known. An infrared wireless keyboard simply uses an infrared transmitter in the keyboard and an infrared receiver in a personal computer to establish an input link from the keyboard to the personal computer. The wireless infrared keyboard does not, of course, need a physical wire connection between the keyboard and the personal computer so that there is no wire clutter.
The infra-red wireless keyboard, however, has numerous drawbacks. Specifically, the infrared wireless keyboard requires a clear line-of-sight between the infrared transmitter in the keyboard and the infra-red receiver in the personal computer. Moreover, the distance between the infrared keyboard and the personal computer must not be too great so that the infrared receiver in the personal computer cannot detect the infrared beam from the infrared transmitter of the wireless keyboard.
The clear line-of-sight and distance requirements constrain the flexibility a that user would desire with regard to a wireless device because an artificial limit is placed on the location and the distance that can exist between the infrared wireless keyboard and the personal computer. In addition, the infrared wireless keyboard has large power consumption requirements because of the infrared transmitter. The infrared wireless keyboard typically operates on a six-volt power source that is commonly derived from four 1.5-volt batteries. Moreover, the increased power consumption reduces overall battery life so that the batteries must be replaced more often.
Conventional radio-frequency ("RF") wireless keyboards addressed some of the shortcomings of the infrared wireless keyboards. Conventional RF wireless keyboards required less power than infrared wireless keyboard, and therefore, provided greater overall battery life so that batteries were replaced less often.
Conventional RF wireless keyboards have drawbacks. One drawback is that the requirement of an RF antenna being large enough so that it is efficient in transmitting RF signals. For example, a conventional RF antenna using electromagnetic propagation principles has a RF antenna that is of the same order of size as the RF wavelength. For example, a 27 MHz signal has a wavelength of eleven meters and would require an antenna of approximately three to six meters for signal transmission. Such a large RF antenna, however, is incompatible with devices such as the wireless keyboard that must be small enough to remain convenient and handy.
To accommodate the requirement of a large antenna without frustrating the advantages of the convenience and handiness of a wireless keyboard, complex and expensive antenna circuitry is incorporated into the conventional RF wireless keyboard. Such circuitry, however, increase the production costs associated with the conventional RF wireless keyboard. Further, the complex and expensive circuitry also increases the power consumption by the system, and therefore, reduces the battery life so that the batteries are replaced more often. Moreover, in some instances even the complex and expensive antenna circuitry still lacks the efficiency for transmitting RF signals that a large RF antenna provided.
Therefore, there is a need for an antenna system for a wireless keyboard that (1) has operational flexibility without physical restraints on communication between the wireless keyboard and a personal computer, (2) is inexpensive to operate and produce without complex and expensive added circuitry, (3) is compact enough to reside within a small housing, (4) consumes less power, and (5) is relatively easy to realize.